1. Field of the Invention
This invention relates to a hardenable composition. Further, this invention relates to a polymer having good film-forming properties. More particularly, this invention relates to heat-curable compositions suitable for paints and printing inks, and comprising a polypentadiene or a pentadienebutadiene copolymer which is modified with epoxy groups and hydroxy groups, of which a part can be esterified to acyloxy groups in some cases.
2. Description of the Prior Art
Previously, chlorinated resins, cellulose nitrate, xylenic resins, polyamide resins, toluenic resins or phenolic resins have been used as film-forming ingredients of thermosetting paints and printing inks.
Although, for example, chlorinated resins have good flame retardancy, chemical resistance and adhesiveness, they have poor weatherability and poor light stability. More particularly, if they are weathered for a long time, they readily change in color or are degraded, and furthermore if they are heated at a high temperature, they begin to decompose into HCl gas and other decomposition substances.
Also, cellulose nitrate has poor weatherability, poor light stability and other poor properties. Worse yet, if it is heated, shocked or exposed to sunshine, it begins to ignite and burn.
Aromatic resins, such as xylenic, toluenic, and phenolic resins, have poor weatherability because of their phenyl moieties.
As another example, a modified polybutadiene containing epoxy groups is described in U.S. Pat. No. 3,253,000. It is an improved film-forming coating resin having good flexibility in comparison with the previously described resins such as aromatic resins, but it has poor weatherability, poor light stability and poor bondability (adhesion), in industrial use.